Motorcycle engines include intake and exhaust valves that are commonly actuated by rotating cams mounted on one or more camshafts. The camshafts are usually driven by the crankshaft, either via meshing gears or via flexible drive elements such as chains or belts.
When a flexible drive element is used, it is important that the drive element be maintained under tension to avoid slapping of the element and to prevent the element from slipping relative to the camshaft or crankshaft. Tensioning of the drive element is frequently accomplished using a tensioner that applies a continuous force on the drive element. The tensioner can include a rotating shoe that spins as it contacts the drive element, or a static shoe that slides relative to the drive element. In either design, wear of the shoe is a concern.
Prior art tensioners are generally made of steel or another metallic substance. From time to time these tensioners wear down due to friction between the drive chain and the tensioner.